Ventilatory sparing strategies and swallowing pattern during bottle feeding in human infants

During feeding, infants have been found to decrease ventilation in proportion to increasing swallowing frequency, presumably as a consequence of neural inhibition of breathing and airway closure during swallowing. To what extent infants decrease ventilatory compromise during feeding by modifying feeding behavior is unknown. We increased swallowing frequency in infants by facilitating formula flow to study potential ventilatory sparing mechanisms. We studied seven full-term healthy infants 5-12 days of age. Nasal air flow and tidal volume were recorded with a nasal flowmeter. Soft fluid-filled catheters in the oropharynx and bottle recorded swallowing and sucking activity, and volume changes in the bottle were continuously measured. Bottle pressure was increased to facilitate formula flow. Low- and high-pressure trials were then compared. With the change from low to high pressure, consumption rate increased, as did sucking and swallowing frequencies. This change reversed on return to low pressure. Under high-pressure conditions, we saw a decrease in minute ventilation as expected. With onset of high pressure, sucking and swallowing volumes increased, whereas duration of airway closure during swallows remained constant. Therefore, increased formula consumption was associated with reduced ventilation, a predictable consequence of increased swallowing frequency. However, when consumption rate was high, the infant also increased swallowing volume, a tactic that is potentially ventilatory sparing as a lower swallowing frequency is required to achieve the increased consumption rate. As well, when consumption rate is low, the sucking-to-swallowing ratio increases, again potentially conserving ventilation by decreasing swallowing frequency much more than if the sucking-to-swallowing ratio was constant.